Typically, gas-operated rifles include a loading mechanism that is driven by ammunition gas pressure generated upon rifle firing and may include a gas piston arranged in a gas cylinder to assist in loading and unloading cartridges. The gas cylinder is at least partially sealed at an end so that a pressure chamber is formed between a gas piston face and a front wall of the gas cylinder. A passage fluidly couples the pressure chamber to the interior of the barrel. After a round is fired and the projectile (e.g., bullet) has passed a connecting point between the pressure chamber and the barrel bore, ammunition gases enter the pressure chamber. The ammunition gases increase a pressure within the pressure chamber and create a resulting force on a face of the piston. The resulting force on the piston acts against a linkage that is part of a loading mechanism and causes the cartridges to feed and eject due to the movement between the piston and the pressure chamber. Additionally, the resulting force on the piston activates (e.g., cocks) the trigger mechanism. The loading mechanism of fully automatic weapons operate as long as the trigger is held in the firing position. A portion of the energy created by firing a cartridge is diverted to operate the loading mechanism.
Typically, the cross-sections governing the flow of the ammunition gases, the piston, and the pressure chamber are designed to match the specifications of a particular firearm that fires at a determined frequency. Specifically, a firing cadence is selected to prevent mechanical overload of the drive mechanism. To maintain the firing cadence, the pressure chamber is provided with a gas outlet that is associated with a pressure setting and a pressure adaptation. Through the gas outlet, the ammunition gases that enter the pressure chamber exit into the environment to reduce the pressure within the pressure chamber. Specifically, the pressure chamber has a lower pressure as compared to the pressure within the barrel. For instance, DE 196 15 181 describes an ammunition gas bleed device.
DE 648 391 describes an adjustable valve that regulates the quantity of ammunition gas that enters the pressure chamber and, thus, the flow and pressure ratios in the ammunition gas bleed arrangement are adaptable to the particular firearm. In some instances, such as during longer sustained continuous fire of an automatic firearm (e.g., a machine gun), the flow and pressure ratios change because the barrel temperature significantly increases. Additionally, the temperature of the ammunition gas within the barrel increases along with the pressure within the barrel. As a result, the pressure within the pressure chamber acting on the gas piston increases, which, in turn, increases the force acting on the gas piston. This increase in pressure accelerates the loading process and increases the force acting on a throttle control rod and the entire loading mechanism.
Accelerating the loading process, increases the firing cadence as well as ammunition consumption. Additionally, the mechanical load on the firearm components increase the wear and tear on the weapon. Unnecessary consumption of ammunition may pose a logistical problem during a military action, because additional ammunition must be brought along and provided at the location that the firearm is being fired without the firearm performance being correspondingly improved.
Adjusting the flow and pressure ratios for stabilization of the cadence of known gas bleed devices is impractical and difficult under operating condition (e.g., firing the weapon). Known methods of maintaining firing cadence stability involves interchanging a second barrel with the hot barrel (e.g., the barrel that is being fired through).
DE 694 12 384 describes a gas feed mechanism for use with semi-automatic weapons and particularly, for use with semi-automatic shotguns. The gas feed mechanism requires a spring-loaded control valve to release gases from the barrel of the weapon to control the gas pressure and to limit the rate of motion of the movable parts.